Then came the sustained drought that ushered in the 21st century, one of the region's periodic dry spells. For five years clouds yielded little moisture, even as the West continued to drink greedily. The Colorado River, lifeblood for seven states, dwindled. Lake Mead and Lake Powell, the river's massive catch basins, shriveled. No amount of hydro-engineering, cloud seeding, flow regulating, or other manipulation could change a simple fact: Not enough water was falling from the sky to keep the West's reservoirs full. Not with the increasing number of straws sucking upstream water to irrigate alfalfa fields, fill swimming pools, and sprinkle suburban bluegrass expanses.

Lake Powell's loss was and is Glen Canyon's unmistakable gain. People who were lucky enough to get a glimpse of Glen Canyon when they were young flocked to see it again, as if offered the chance to visit, after 40 years, a first love who had abruptly moved away. People who had only known the canyon through photos and descriptions—by John Wesley Powell, Wallace Stegner, Katie Lee, Eliot Porter, David Brower, and Edward Abbey—hurried for a first look.

The ancient Navajo sandstone itself shook off the water as easily as a dog emerging from a swimming pool. At an average rate of an inch a day, a lost sculpture garden of rock resurfaced, miraculously intact.

The uncovered slickrock sandstone told its astounding life story: of Sahara-size sand dunes marching across the landscape 190 million years ago; of three-toed dinosaurs that left tracks in damp spots between the dunes; of deep burial that slowly squeezed sand and mud into rock; of epic uplifts and tectonic shifts; of water and wind that carved slot canyons hundreds of feet deep.

Layers of human history saw the light again too: thousand-year-old petroglyph panels and cave dwellings of the Anasazi; artifacts from Navajo settlements; inscriptions left by 19th-century Mormon pioneers; equipment from uranium miners' camps of the 1950s; sunken boats and even a lost airplane of more recent vintage.

Desert varnishes, mineral-rich dust transformed by microbes and moisture, soon streaked the canyon walls. Vermilion, rust, beige, taupe, slate, maroon, cocoa, coffee, pale orange, and peach, they began painting over the lake-bleached bathtub ring left by high water. Streams rippled anew in the side canyons that branch out like arteries from the main stem of the Colorado to distribute life—maidenhair ferns and coyote willow, soft-stem bulrushes and golden sedges—in this arid land.